176 IRRIGATION PRACTICE 



at planting time, for (1) it makes possible a quicker and 

 more complete germination, and (2) it delays the time 

 of the first irrigation, and the plant is enabled to estab- 

 lish a strong root-system. It is, also, decidedly advanta- 

 geous to keep the soil well saturated with water through- 

 out the dormant season. Water added in. the fall dis- 

 tributes itself in the usual way throughout the soil to a 

 considerable depth. The soil- water film then remains 

 long in intimate contact with the soil particles; plant- 

 food is dissolved and well distributed throughout the 

 water until, at planting time, the soil-water is heavily 

 charged with dissolved plant-food and is a very nutri- 

 tious medium for plant-growth. 



Water applied during the growing season is imme- 

 diately drawn upon by the plant, and does not remain in 

 the soil long enough to permit of extensive solution or 

 distribution of soil nutrients in the soil-moisture film. 

 Only the portions of the soil-water film that lie nearest 

 to the soil particles become rich in plant-food. This may 

 be the one explanation of the repeated observation that 

 a given quantity of water applied in irrigations at inter- 

 vals of one, two, three or even four weeks may often 

 yield a larger crop than when applied in smaller and more 

 frequent irrigations. Water applied too frequently or in 

 small quantities is pumped out of the soil so rapidly 

 that there is little chance for solution of plant-food. 

 With longer intervals and larger irrigations, more plant- 

 food may be dissolved and used in plant-production. 



At any rate, water applied in the fall and winter sea- 

 son has the opportunity throughout the long months of 

 the dormant season to dissolve from the soil such materials 

 as will be of value in plant-growth. Such soil solution is 

 of tremendous value in establishing the young plant dur- 



